high frequency fast response buck controller

Hi Team,

my customer need an high frequency fast response buck controller, their requirement is: input 80V, output 40V, 2A, power on/power off slop is about 20us. ripple is about 10mVpp.

As very low output ripple/very quick power on-off time, so they need high frequency(like 2MHz or higher) fast response buck controller, they can use GaN FET and driver, they can use LDO to power for controller, so could you help on suggest one or two part for this application?

Thanks very much.

Regards, Sunny